Systems and Methods for Bypass Operation of Variable-Speed Drive

Abstract

A heating, ventilation, and air conditioning (HVAC) unit including a variable-speed drive and a bypass circuit is provided. Under normal operation, the drive receives line voltages as inputs and provides variable-speed control signals to components of the HVAC unit (for example, a compressor, fan motor, etc.). The drive allows the HVAC to operate at below maximum capacity, which increases the efficiency of the HVAC unit. When a fault condition is detected in the drive, the HVAC unit automatically switches to the bypass circuit such that the line voltages are provided directly to the components. This results in the HVAC unit operating at maximum capacity for a period of time, but allows the HVAC unit to continue operation even when the drive is experiencing the fault condition.

That which is claimed is: 
     
         1 . A heating, ventilation, and air conditioning (HVAC) unit comprising:
 a compressor;   a drive configured to:
 receive a constant line voltage as an input; and 
 output, to the compressor and using a first circuit, a control signal, the control signal comprising a second voltage that is different than the constant line voltage, wherein the control signal is a variable-speed control signal or a variable-frequency control signal; 
   one or more processors; and   memory storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to:
 determine that a fault condition has occurred in the drive; and 
 send a first signal to close one or more contacts associated with a second circuit, wherein closing the one or more contacts causes the constant line voltage to be received by the compressor instead of the control signal from the drive. 
   
     
     
         2 . The HVAC unit of  claim 1 , wherein the computer-executable instructions further cause the one or more processors to:
 determine that the fault condition is no longer present in the drive; and   send a second signal to open the one or more contacts associated with the second circuit.   
     
     
         3 . The HVAC unit of  claim 1 , further comprising:
 a dual capacitor comprising a first capacitor and a second capacitor, wherein the first capacitor is associated with the first circuit and the second capacitor is associated with the second circuit.   
     
     
         4 . The HVAC unit of  claim 1 , wherein the computer-executable instructions further cause the one or more processors to:
 send an alert indicating the fault condition in the drive.   
     
     
         5 . The HVAC unit of  claim 1 , wherein the fault condition is determined based on at least one of: a value associated with a register of the drive or data received from a sensor of the HVAC unit. 
     
     
         6 . The HVAC unit of  claim 1 ,. 
     
     
         7 . The HVAC unit of  claim 1 , wherein the compressor is a two-stage compressor, and wherein the compressor is operated using the drive at a first frequency, and wherein the compressor is operated without using the drive at a second frequency. 
     
     
         8 . A method comprising:
 determining, by a controller, that a fault condition has occurred in a drive of an HVAC unit, wherein the drive is configured to receive a constant line voltage as an input, and wherein the drive is further configured to output, to a compressor of the HVAC unit and through a first circuit, a control signal, the control signal comprising a second voltage that is different than the constant line voltage, wherein the control signal is a variable-speed control signal or a variable-frequency control signal; and   sending a first signal to close one or more contacts associated with a second circuit, wherein closing the one or more contacts causes the constant line voltage to be provided directly to the compressor instead of the control signal from the drive.   
     
     
         9 . The method of  claim 8 , further comprising:
 determining that the fault condition is no longer present in the drive; and   sending a second signal to open the one or more contacts associated with the second circuit.   
     
     
         10 . The method of  claim 8 , wherein the HVAC unit further comprises a dual capacitor comprising a first capacitor and a second capacitor, wherein the first capacitor is associated with the first circuit and the second capacitor is associated with the second circuit. 
     
     
         11 . The method of  claim 8 , further comprising:
 send an alert indicating the fault condition in the drive.   
     
     
         12 . The method of  claim 8 , wherein the fault condition is determined based on a value associated with a register of the drive. 
     
     
         13 . The method of  claim 8 , wherein determining the fault condition is based on data associated with a sensor of the HVAC unit. 
     
     
         14 . The method of  claim 8 , wherein causing to send the first signal is based on a manual input to a button or switch on the HVAC unit. 
     
     
         15 . An apparatus comprising:
 a compressor;   a drive configured to:
 receive a constant line voltage as an input; and 
 output, to the compressor and using a first circuit, a control signal, the control signal comprising a second voltage that is different than the constant line voltage, wherein the control signal is a variable-speed control signal or a variable-frequency control signal; and 
   a controller configured to:   determine that a fault condition has occurred in the drive; and   send a first signal to close one or more contacts associated with a second circuit, wherein closing the one or more contacts causes the constant line voltage to be received by the compressor instead of the control signal from the drive.   
     
     
         16 . The apparatus of  claim 15 , wherein the controller is further configured to:
 determine that the fault condition is no longer present in the drive; and   send a second signal to open the one or more contacts associated with the second circuit.   
     
     
         17 . The apparatus of  claim 15 , further comprising a dual capacitor comprising a first capacitor and a second capacitor, wherein the first capacitor is associated with the first circuit and the second capacitor is associated with the second circuit. 
     
     
         18 . The apparatus of  claim 15 , wherein the controller is further configured to:
 send an alert indicating the fault condition in the drive.   
     
     
         19 . The apparatus of  claim 15 , wherein the fault condition is determined based on a value associated with a register of the drive. 
     
     
         20 . The apparatus of  claim 15 , wherein determine the fault condition is based on data associated with a sensor of the apparatus.